The above schematic lays out the theory, but I just don't know what to make of that 4th pin discrepancy. KEEPING THINGS COOL Maximize cooling efficiency with powerful fan speeds and PWM fan control to quickly lower system temperatures when needed and staying quiet under light loads. Unfortunately, I don't have a multimetre or anyone to borrow one from. Sync with your motherboard for direct control using RGB software, including Chroma. It's not my picture, I just posted it because it shows the same connector key ridges layouts side by side, left is how the HP fan is, keys on either side, right's a regular PWM. Judging by the below diagram, the first three pins should be fine, but it's that last ' or +5V' bit on the fourth pin that has me worried - forgive me, my electronics lessons are long behind me, but if the motherboard 'puts' that 5V on the 4th pin where the Noctua's expecting a PWM signal, would that cause a problem? Noctua's got a little article here outlining the two different solutions, but they don't actually spell out whether I can safely plug a PWM fan in a DC header. I guess my main question is - ignoring the ridges, which I could just file off, would plugging a 4-pin PWM fan in a non-PWM, voltage-controlled 4-pin header still work properly or at all? Both the HP fan and the Noctua are listed as 12V and HP won't have developed their own new standard, so that header's gotta be either PWM or DC-based. Unlike traditional motherboards that use analog power, this motherboard uses a next generation digital PWM (Pulse-Width Modulation) design, which provides. Click to expand.It's not my picture, I just posted it because it shows the same connector key ridges layouts side by side, left is how the HP fan is, keys on either side, right's a regular PWM.

Pwm fan motherboard